Multibeam convergence controlling system



May 11, 1954 H. c. GooDRlcH MULTxBEAM CONVERGENCE coNTRoLLING SYSTEM Filed July 25', 1952 Patented May 11, 1954 MULTIBEAM CONVERGENCE CONTROLLING SYSTEM Hunter C. Goodrich, Collingswood, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application July 23, 1952, Serial No. 300,423

Claims. 1

This invention relates to systems for controlling the electron beam energy of cathode ray tubes. It pertains particularly to the control of a plurality of electron beam components used in television kinescopes so as to eiiect substantial convergence of the components at all points of a raster scanned in a predetermined plane.

One type of cathode ray tube in which there is encountered the problem of maintaining substantial convergence of a plurality of beam components in the plane of a target electrode is a color kinescope such as that disclosed in a paper by H. B. Law titled A 'I'hree-Gun Shadow-Mask Color Kinescope published in the Proceedings of the IRE, vol. 39, No. 10, October 1951 at page 1186. Such a tube has a luminescent screen consisting of a multiplicity of phosphor areas of sub-elemental dimensions. Diferent ones of the phosphor areas are capable oi' producing light of the component image colors when excited by electron beam energy. In this tube, the diierent light-producing phosphor areas are excited respectively by a plurality of electro-n beams, or by a plurality of components of a single beam, approaching the screen from different angles through an apertured electrode. Color selection is secured by the angle at which the electron beam components approach the screen. A tube oi the kind described forms the subject matter of U. S. Patent 2,595,548 granted May 6, 1952 to Alfred C. Schroeder for Picture Reproducing Apparatus.

The expression electron beam components as used in this specication and claims will be understood to denote the phosphor-exciting electronic energy produced either by a single, or by a plurality of, electron guns. This energy may be continuous or pulsating as required Without departing from the scope of the invention. An example of a color kinescope in which diierent components of a single electron beam are used to excite a phosphor screen of the kind described is disclosed in a paper by R. R. Law, titled A One-Gun Shadow-Mask Color Kinescope published in the Proceedings of the IRE, vol. 39, No. i0, October 1951, at page 1194. Such a tube forms the subject matter of a copending U. S. application oi Russell R. Law, Serial No. 165,552, iiled June 1, 1950 and titled Color Television.

The successful operation of a multi-color kinescope of the type referred to requires that the plurality of electron beam components be made to converge substantially in the plane of the aperture electrode at all points in the scanned raster. In View of the fact that the diiierent points of such a target electrode are at different distances from the point or region of the electron beam deflection, it is necessary to provide a eld-produ'cing means which is variably energized to produce the desired dynamic convergence control. One such electron beam control system is disclosed in a paper by Albert W. Friend titled Deilection and Convergence in Color Kinescopes published in the Proceedings of the IRE, vol. 39, No. 10, October 1951 at page 1249. Such a system forms the subject matter of a copending U. S. application of Albert W. Friend, Serial No. 164,444, riled May 26, 1950 and titled Electron Beam Controlling System. In the system proposed by Friend, electron-optical apparatus is energized both statically and dynamically to produce the desired result. By means including the static energization of the electron-optical apparatus, the Friend system effects initial convergence of the electron beam components substantially at the center of the raster to be scanned. The dynamic energization of the electron-optical apparatus is effected as functions of both the horizontal and vertical beam deection. Essentially these functions are parabolic. YIn the Friend and other systems previously employed, somewhat complicated apparatus has been required to produce the desired energizing Waveforms, particularly at the vertical deflection frequency.

Therefore, it is an object of this invention to provide improved and simplified apparatus by which to develop waveforms for the dynamic energization of an electron beam-controlling system for a multi-beam kinescope.

Another object of the invention is to provide improved apparatus by which to develop, directly from the deection apparatus, waveforms for effecting dynamic convergence of the electron beam components of a multi-beam kinescope.

In accordance With this invention there is provided Wave-generating apparatus having an input circuit which may be coupled directly to the deiiection apparatus and which requires no additional amplification so that it may be coupledI to the iield-producing electron-optical apparatus by means of which beam `convergence is to be effected. The apparatus embodying the invention comprises a convergence Wave output transformer having its primary winding coupled to the anode of an electron tube serving as the output stage for one of the electron beam deflection waves by means of which the electron beams are deflected to scan the usual rectangular raster at a target electrode. The secondary Winding of the convergence transformer is coupled to the field-producing, or electron-optical, apparatus for the energization thereof, whereby to effect the desired electron beam convergence. The primary transformer winding has a capacitor connected thereto so as to effect an integration of the sawtooth wave deiiection energy and therebyT to produce a substantially parabolic wave. This parabolic wave has an amplitude which is adequate without further amplication to effect the desired energization of the electron-optical beam convergence apparatus.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in conjunction with the accompanying drawings, in which:

Figure 1 is a circuit diagram, mostly in block form except for the illustrated details of the apparatus embodying the present invention, for developing a beam convergence wave for use with electron-optical beam-converging apparatus of an electrostatic type;

Figure 2 is a fragmentary circuit diagram of that portion of the dynamic convergence waveproducing apparatus embodying this invention showing apparatus for impressing the developed wave upon an electromagnetic type of electronoptical beam convergence apparatus; and,

Figure 3 is another fragmentary circuit diagram showing the use of apparatus embodying .this invention in another type of deflection wave output circuit.

Reference first will be made to Figure l of the drawings for a description of an illustrative embodiment of the invention. The television receiver represented in this ligure is generally conventional and includes an antenna II to which is coupled a conventional television signal receiver I2. It will be understood that the receiver l2 may include such usual apparatus as carrier wave amplifiers at both radio and intermediate frequencies, a frequency converter and a carrier wave demodulator or signal detector. Accord- '-ingly, it will be understood that there are derived from the receiver I2 the video and synchronizing signals. The video signals derived from the receiver I2 are impressed upon a video signal channel I3 and the synchronizing signals are impressed upon a sync signal separator I4. The video signal channel is coupled to the usual electron beam control apparatus, customarily referred to as electron gun apparatus, of an imagereproducing device such as a kinescope I5.

In the illustrative embodiment of the invention, it is assumed that the invention is used in a color television system. In this case, the kinescope is of the same general type disclosed in the I-I. B. Law paper previously ref-erred to. It will be understood, however, that the kinescope alternatively may be of other types such as that shown in the aforementioned R. R. Law paper. -In either case, however, the kinescope has a substantially nat luminescent screen I6 which is provided with a multiplicity of small phosphor areas arranged in groups and capable respectively of producing light of the different primary colors in which the image is to be reproduced when excited by electron beam energy. In back of, and spaced from the screen I6, there is an apertured masking electrode I'I having an aperture for, and in alignment with, each group of phosphor areas of the screen I6. In the particular tube illustrated, the kinescope also has a plurality lof electron guns I8, I9 and 20, equal in number to the number of primary colors in which the image is to be reproduced. As previously indicated, these three electron guns are coupled to the video signal channel I3 for respective control by video signals representing the three primary colors in which the image is to be reproduced. It will be understood that each of these guns may be conventional consisting of a cathode, a control grid, and a first anode, or beamforming electrode. Also associated with the three electron guns are corresponding individual beamfocusing anodes 22, 23 and 24. The three electron guns I8, I 9 and 20, together with their associated focusing electrodes 22, 23 and 24 respectively, function to.develop respective electron beams 25, 26 and 21 which are caused to approach the target electrode structure, including the luminescent screen I6 and the masking electrode II, from three different angles which, for convenience, have been shown greatly exaggerated in the drawing. By means of the different angles of approach these beams are caused to excite the different colored light-producing phosphors.

The color kinescope I5 additionally is provided with an electrostatic type of beam-converging apparatus which includes a convergence anode 28 located adjacent the paths followed by the electron beams in the predeflection region. The kinescope also includes the usual final, or beamaccelerating, anode 29 generally in the form of a wall coating substantially as shown and extending from the predeection region adjacent to the convergence anode 28 to the vicinity of the target electrode structure including the screen I5.

The different static potentials which are impressed upon the various kinescope electrodes are derived from a power supply 3|, across the terminals of which is connected a voltage divider resistor 32. The various electrode potentials are 'derived by making suitable connections to the voltage divider resistor generally in the manner shown. The individual beam-focusing electrodes 22, 23 and 24 are connected together with and to a relatively low positive potential point on the voltage divider resistor 32. The convergence anode 28 is coupled to a somewhat higher positive potential point of the resistor 32 so that, as a result of the potential difference between it and the individual beam focusing anodes 22, 23 and 24, there are produced electrostatic electron-optical lenses by which individual beam focusing is effected. In a like manner, the final anode 29 is connected to a relatively high positive potential point on the voltage divider ref sistor 32 so as to create another electron-optical lens with the convergence anode 28. The purpose of this latter electron-optical device is to produce the desired convergence of the individual electron beams substantially in the plane of the 1 apertured electrode I1.

The color kinescope I5 also is provided with apparatus by which to deflect the plurality of electron beam components both vertically and horizontally to scan the usual raster at the luminescent screen I6. In this embodiment of the invention the deflection apparatus includes a yoke 33 which in general is of a conventional type. It consists of a pair of interconnected coils forming a horizontal deflection winding and another pair of coils forming a vertical deflection winding.

The yolre is mounted around the neck of the lrinescope in the region adjacent to the point at which the neck joins the conical section of the tube. The horizontal and vertical windings of the yoke 33 are energized by substantially conventional apparatus. The sync signal separator it, which separates the sync signals from the video signals and from one another, produces horizontal and vertical frequency sync signals respectively in its output circuits H and V. The horizontal output circuit H is coupled to a horizontal sweep oscillator 34, the output of which, in

turn, is coupled to the input circuit of a horizontal sweep output apparatus 35. Both of these horizontal sweep components may be entirely conventional. The output circuit of the horizontal sweep output apparatus 35 is coupled to the horizontal deflection winding of the yoke 33 in the customary manner.

The vertical sync separator output circuit V is coupled to a vertical sweep oscillator 36 which produces in its output circuit a substantially sawtooth wave such as 3l at the vertical deflection frequency. The output of the vertical sweep oscillator is coupled to the input circuit of a vertical sweep output stage including an electron tube 38. This tube may be a pentode, such as a SKG-GT, or a bearn power tetrode, such as a GUS or its miniature equivalent a 6AQ5, or other similar tube types which are extensively used in conventional vertical sweep output apparatus. The anode of the vertical output tube 38 is coupled to the primary winding 39 of a vertical deiiection wave output transformer dil, also as is customary in such systems. The secondary winding lll of the vertical output transformer M3 is connected to the vertical deflection winding of the yoke 33. A bypassed variable cathode resistor i12 serves as a linearity control of the vertical deflection wave.

As a feature of the present invention, the screen grid 43 of the vertical output tube 3S, instead of being connected directly to the anode of the tube or to a source of positive potential, is connected to one terminal of the primary winding 44 of a vertical convergence step-up output transformer 45. The other terminal of the primary winding llt is connected to the anode of the vertical output tube 33. The secondary winding e5 of the vertical convergence output transformer 45 is coupled by a capacitor il to the convergence anode 2s of the color kinescope l5. The other terminal of the secondary winding 46 is connected to ground through an amplitude-controlling potentiometer, or variable resistor d8. A bleeder resistor 48 is coupled across the secondary winding 45 of the vertical convergence output transformer, and a point on this resistor is coupled by a capacitor 5! to the individual beam-focusing anodes 22, 23 and 25..

As another feature of the present invention, the primary winding s4 of the vertical output transformer 55 has connected in shunt therewith, an integrating capacitor 52 and, if desired, a variable wave-shaping resistor 53. The capacitor 52 functions in a manner to be described, in conjunction with other components of the circuit, to convert the substantially sawtooth current wave 3'! flowing through the vertical output tube '3d into a substantially parabolic voltage wave 5d in the secondary winding d6 of the vertical convergence transformer 35. The time constant of the capacitor 52 and the resistance reflected to the primary winding Mi should be of the same order of magnitude as a vertical deflection period. The variable resistor 53 may be included to effect some additional shaping of the parabolic wave 54.

The beam convergence controlling system embodying this invention also includes a horizontal convergence control wave generator 55. This apparatus may be substantially in accordance with that disclosed in the Friend paper previously referred to. Accordingly, it will be understood that this generator functions to produce a substantially parabolic wave 56 at the horizontal deflection frequency for impression by means such as a coupling capacitor 5l' upon the convergence anode 2e of the color kinescope l5.

The manner in which the vertical convergence control wave-generating apparatus functions is substantially as follows: The flow of the substantially sawtooth plate current wave 3'! through the capacitor 52 results in an integration thereof, producing the substantially parabolic voltage wave 54 in the secondary winding 46. The turns ratio of the primary and secondary windings :is and d, respectively, of the vertical convergence output transformer 45 is such that the load which is reiiected from the secondary to the primary winding is essentially resistive, having a value which is several times that of the rea-ctance of the integrating capacitor 52. at the vertical denection frequency. Accordingly, this loading does not appreciably alter the waveform produced across the integrating capacitor 52. Thus, since the load upon the secondary winding 45 also is predominantly resistive, the convergence voltage wave 54 is substantially parabolic.

At the same time, it will be understood that the current wave produced in the secondary winding il of the vertical deflection output transformer El is not appreciably affected by the parabolic Wave-forming apparatus described and, therefore, has essentially a sawtooth form 58. The voltage at the anode of the tube 33 has Very little inuence upon the anode and the screen grid currents. Therefore, the presence of the parabolic wave in the primary transformer winding d4 does not noticeably affect-the linearity of vertical beam deflection.

In the operation of the apparatus, it functions to produce the parabolic voltage wave 54 when the shaping resistor 53 has a substantially zero value. An increase in the value of the resistor 53 effects the introduction of a sawtooth component into the otherwise parabolic wave 54 for the purpose of compensating for slight dissyrnmetries in the beam convergence requirements. The variable resistor 43 may be adjusted to effect a control of the peak-to-peak amplitude of the substantially parabolic wave 5e.

The substantially parabolic wave El, developed in themanner described, may be impressed, not only upon the convergence anode 28. but also in suitable magnitude upon the individual beamfocusing anodes 22, 23 and 24 as described. The purpose of such an arrangement is to prevent a defocusing of the individual electron beams which tends to occur when the potentials impressed upon the individual beam-focusing anodes is maintained constant and the potential of the convergence anode is varied. This provision, however, is not part of the present invention. lnstead, it forms the subject matter of a copending U. S. application of L. R. Kirkwood, Serial No. 198,313 led Novembery 30, 1950 and titled Dynamic Electron Beam Control Systems.

The present invention may also be utilized for dynamic beam convergence systems in which the electron-optical beam-converging apparatus is of the electromagnetic type. Figure 2, to which reference now will be made, shows an illustrative way of coupling the beam convergence controlling wave-generating apparatus in accordance with this invention to such a convergence system. It will be understood that the Wave-generating apparatus may be of the same character as that described with reference to Figure 1. In this case, the kinescope l is provided with a magnetic convergence coil 59 in place of, and in substantially the same predeflection region occupied by, the convergence anode 28 of Figure 1. The convergence coil 59 is connected to the secondary winding of the vertical convergence output transformer 45 through the amplitude-controlling resistor 48. Suitable provision also may be made, in this case, if desired, to connect the individual beam-focusing anodes 22, 23, and 24 to the output circuit including the secondary winding 48.

Apparatus in accordance with the present invention also may be used in other types of deflection wave output circuits, such as the one shown in Figure 3 to which reference now will be made. The principal difference between this output circuit and the one shown in Figure l is that the Screen grid of the vertical sweep output tube 33, instead of being connected through the primary Winding 39 of the vertical output transformer 4B for the impression thereon of a positive potential, is connected directly to a source of positive potential. In the case of the apparatus of Figure 3, it is seen that the current owing in the circuit of the screen grid 43 does not traverse the primary winding of the output transformer as it does in the case of the apparatus of Figure 1.

It may be seen from a consideration of the foregoing description of the illustrative embodiments of the invention that there is provided an improved and considerably simplified apparatus by which to develop the waveforms, particularly at vertical deflecting frequencies, for the dynamic energization of the electron beam-controlling apparatus of a multi-beam kinescope. A large measure of the simplicity of the apparatus embodying the invention is achieved by reason of the ability of the apparatus to operate directly from the raster-scanning deflection apparatus without requiring any additional amplification. Also, this invention lends itself to use, not only with beam tetrodes as described which previously have been connected as triodes for conventional vertical deflection of the electron beams, but also with vertical output tube connections of the character in which only the plate current flows through the deiection output transformer. The only diiference is that in one case, such as the one described with reference to Figure 1, the screen grid current flows through the deflection transformer primary winding 39, together with the anode current of the tube 38, Whereas in the other case, such as the one described with reference to Figure 3, only the anode current of the output tube flows in the output transformer winding.

The nature of the invention may be ascertained from the foregoing description of a number of illustrative embodiments thereof. Its scope is pointed out in the appended claims.

What is claimed is:

1. In a cathode ray image-reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said field-producing means comprising, a raster-scanning substantially sawtooth deflection wave generator comprising an output circuit including an electron tube having an anode coupled to said deflection wave output circuit, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence wave output circuit coupling said secondary winding to said fieldproducing means, means coupling said primary winding to said electron tube anode, and an integrating capacitor connected to said primary winding to convert some of the energy of said sawtooth wave to a substantially parabolic Wave in said secondary winding.

2. In a cathode ray image-reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angular-ly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to eifect substantial convergence of said beam components at all points of said raster, a system to energize said field-producing means comprising, a raster-scanning substantially sawtooth deflection wave generator comprising an output circuit including an electron tube having an anode coupled to said deflection Wave output circuit, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence wave output circuit including a. variable amplitude-adjusting resistor and coupling said secondary winding to said fieldproducing means, means coupling said primary winding to said electron tube anode, and an integrating capacitor connected in shunt with said primary winding to convert some of the energy of said sawtooth Wave to a substantially parabolic wave in said secondary winding.

3. In a cathode ray image-reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said field-producing means comprising, a raster-scanning substantially sawtooth deflection wave generator comprising an output circuit including an electron tube having an anode coupled to said deflection wave output circuit, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence wave output circuit including a series-connected variable amplitudeadjusting resistor and coupling said secondary winding to said field-producing means, means coupling said primary winding to said electron tube anode, and a series connection of an integrating capacitor and a variable Wave-shaping resistor connected in shunt with said primary winding to convert some of the energy of said sawtooth wave to a Wave in said secondary winding having a substantially parabolic shape modified by a sawtooth component of a magnitude determined by the adjustment of said waveshaping resistor.

4. In a cathode ray image-reproducing system wherein a plurality of electron beam components, which traverse predeection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and` energizable to effect substantial convergence of said beam components at all points of said raster, a system tc energize said field-producing means comprising, a raster-scanning substantially sawtooth deflection wave generator having an output circuit including a transformer, an electron tube having an anode coupled to said deflection wave output transformer, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence wave output circuit coupling said secondary winding to said field-producing means, means coupling said primary winding to said electron tube anode in series with said deflection wave output transformer, and an integrating capacitor connected in shunt with said primary winding to convert some of the energy of said sawtooth wave to a substantially parabolic wave in said secondary winding.

5. In a cathode ray image-reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of the tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said field-producing means comprising, a raster-scanning substantially sawtooth deflection wave generator having an output circuit including a transformer, an electron tube having an anode coupled to said deflection wave output transformer, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence wave output circuit coupling said secondary winding to said field-producing means, means coupling said primary winding to said electron tube anode in series with said deflection wave output transformer, an integrating capacitor connected in shunt with said primary winding to convert some of the energy of said sawtooth wave to a substantially parabolic wave in said secondary winding, and a variable resistor connected in series with said integrating capacitor to modify said parabolic wave by a sawtooth component.

6. An energizing system for field-producing means as dened in claim wherein, the turns ratio of said convergence wave output transformer primary and secondary windings is of a character to reflect a resistive load to said primary winding having a value several times greater than that of the reactance of said integrating capacitor at said electron beam deflection frequency.

7. An energizing system for field-producing means as defined in claim 5 wherein, said electron tube also is provided with a screen grid connected for the impression of a positive potential thereon to a point in said series circuit between said primary convergence output transformer winding and said deflection wave output transformer.

8. An energizing system for field-producing means as dened in claim 5 wherein, said electron tube also is provided with a screen grid connected directly to a source of positive potential.

9. In a cathode ray image-reproducing system wherein a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of the tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having electrostatic fieldproducing means including a convergence anode adjacent to said predeflection paths and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said convergence anode cornprising, a raster-scanning substantially sawtooth deflection wave generator having an output circuit including a transformer, an electron tube having an anode coupled to said deflection wave output transformer, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence wave output circuit capacitively coupling said secondary winding to said convergence anode, means coupling said primary winding to said electron tube anode in series with said deection wave output transformer, and an integrating capacitor connected in shunt with said primary winding to convert some of the energy of said sawtooth wave to a substantially parabolic wave in said secondary winding.

10. In a cathode ray image-reproducing system. wherein a plurality of electron beam components, which traverse predeection paths that are spaced respectively about the longitudinal axis of the tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having electromagnetic field-producing means including a convergence coil adjacent to said predeection paths and energizable to effect substantial convergence of said beam components at all points of said raster, a system to energize said convergence coil comprising, a raster-scanning substantially sawtooth deflection wave generator having an output circuit including a transformer, an electron tube having an anode coupled to said deflection wave output transformer, a convergence wave output transformer having primary and secondary windings, a predominantly resistive convergence Wave output circuit conductively coupling said secondary winding to said field-producing means, means coupling said primary winding to said electron tube anode in series with said deflection wave output transformer, and an integrating capacitor connected in shunt with said primary winding to convert some of the energy of said sawtooth wave to a substantially parabolic wave in said secondary winding.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,083,203 Schlesinger June 8, 1937 2,165,028 Blumlen July 4, 1939 2,449,524 Witherby Sept. 14, 1948 2,510,027 Torsch May 30, 1950 2,619,612 Lawrence Nov. 25, 1952 2,623,195 Best Dec. 23, 1952 

